1. Field of Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile device, a composite machine, or the like, employing a xerography method or an electrostatic recording method, and a cleaner and a cleaning blade used in the image forming apparatus and, more particularly, an image forming apparatus capable of preventing generation of the defective cleaning when almost spherical toners are employed as the developer and a cleaner and a cleaning blade.
2. Description of Related Art
As the almost spherical toner cleaning method in the prior art, the method of employing the almost spherical toners and the unshaped toners that are mixed at a particular rate (for example, JP-A-Hei.8-62893, JP-A-Hei.8-95286) is proposed. However, in the case of such method, since the almost spherical toners also pass through clearances between the unshaped toners to go to the blade edge portion, the improvement in the defective cleaning of the almost spherical toners is not sufficient.
The inventors of the present invention thought the above defective cleaning could be overcome by using a cleaning blade having a high rebound resilience, and then made the study.
As the result of the study of the inventors of the present invention, it is found that, if the modulus of repulsion elasticity of a cleaning blade made of a urethane rubber is not less than 20% in a low-temperature/low-humidity atmosphere, the above drawback can be improved. In such case, however, if the modulus of repulsion elasticity in the low-temperature/low-humidity atmosphere is set too high, sometimes a broken edge or the turned-up edge of the cleaning blade is generated due to the change in the rubber characteristics, in a high-temperature/high-humidity (28xc2x0 C., 85% RH) atmosphere.
In order to prevent the broken edge, of the cleaning blade made of a urethane rubber in the above high-temperature/high-humidity atmosphere, the inventors of the present invention have confirmed as the results of the studies, if the blade having the modulus of repulsion elasticity of not less than 20% at 10xc2x0 C. and not more than 70% at 40xc2x0 C. is employed, both the defective cleaning in the low-temperature/low-humidity atmosphere and the broken edge of the cleaning blade in the high-temperature/high-humidity atmosphere can be improved. However, in the cleaning blade whose modulus of repulsion elasticity is within the above range, such cleaning blade can merely attain the improvement of the drawback but cannot get to the settlement. Therefore, the inventors of the present invention repeated earnestly the study and the examination confirmed that, since the value of either the 300% modulus or the tear strength of the cleaning blade or both values of them are still low, the above drawback has not been overcome.
Also, if the cleaning blade that is pushed against the image carrying body is used for a long time in the high-temperature and high-humidity atmosphere, such cleaning blade is set permanently (settling). If the cleaning blade is set, the pushing force of the cleaning blade against the image carrying body is lowered. Thus, there is the problem that the defective cleaning is generated. The inventors of the present invention made the studies and the examinations about this problem, and then confirmed that the above problem can be overcome by suppressing the permanent elongation of the cleaning blade.
The present invention has been made in view of the above problem and studies, and has a following content (1) as a subject.
(1) To provide a cleaning blade, a cleaner, and an image forming apparatus capable of preventing sufficiently the defective cleaning of almost spherical toners without fail from the low-temperature and low-humidity atmosphere to the high-temperature and high-humidity atmosphere.
Next, the present invention created to overcome the above subjects will be explained hereunder. In order to facilitate the correspondence to elements of Examples described later, symbols of the elements in the Examples that are given in parenthesis are added to the elements of the present invention. In this case, the reason for explaining the present invention to correlate with the symbols of the Examples described later is to make the understanding of the present invention easy, and not to intend to limit the scope of the present invention to the Examples.
In order to overcome the above subject, a cleaning blade (3) according to a first aspect of the invention has a blade top end portion for frictionally contacting with a surface of an image carrying body (PRy to PRk, B) to remove residual toners on the surface when the surface rotating passes through a cleaning area. The cleaning blade (3) is made of elastic material. The cleaning blade (3) is formed of urethane rubber. A modulus of repulsion elasticity (JIS K6255) of the cleaning blade (3) is not less than 20% at 10xc2x0 C. and not more than 70% at 40xc2x0 C. A 300% modulus (JIS K6251) of the cleaning blade (3) is not less than 200 kgf/cm2. A tear strength (JIS K6252 crescent type) of the cleaning blade (3) is more than 35 kgf/cm.
In the cleaning blade (3) of the present invention, a tension set (JIS K6262) is preferably not more than 2.5% (a second aspect of the invention), more preferably not more than 1.0%, and still more preferably not more than 0.5%.
Normally, if the shape factor SF of the toner used in the image forming apparatus (U) is SF less than 140, the defective cleaning is ready to occur as the SF (shape factor) value is reduced. Also, in the cleaning blade (3) in the prior art, in order to assure the cleaning performance in the low-temperature and low-humidity atmosphere, the pushing force of the cleaning blade (3) against the photoreceptors (PRy to PRk, B) must be increased. However, there is the problem that, if the pushing force is increased, the worn amount of the surface layer of the photoreceptors (PRy to PRk, B) is increased and thus the life of the photoreceptors (PRy to PRk, B) is shortened.
However, in the cleaning blade (3) of the present invention having the above configuration, since the cleaning blade (3) having the modulus of repulsion elasticity (JIS K6255) of 20% at 10xc2x0 C. and 40% at 40xc2x0 C. is used, the temperature dependency (variation) is small. In this case, if the cleaning blade (3) having the relatively high modulus of repulsion elasticity on the low temperature side is used to improve the cleaning characteristic in the low-temperature and low-humidity atmosphere, the modulus of repulsion elasticity on the high temperature side can be set to the relatively low value. As a result, since the material having the relatively high modulus of repulsion elasticity on the low temperature side can be employed, the cleaning performance can be assured unless the pushing force applied on the low temperature side is enhanced. Also, since the modulus of repulsion elasticity on the high temperature side is suppressed, the burr or the break of the cleaning blade (3) caused in the high-temperature and high-humidity atmosphere can be suppressed.
Also, in the present invention, the 300% modulus (JIS K6251) is 230 kgf/cm2, and the tear strength (JIS K6252 crescent type) is 35 kgf/cm. In this manner, if the 300% modulus and the tear strength are high, the minute chip of the cleaning blade (3) can be suppressed and particularly the cleaning performance at SF less than 140 can be improved.
In addition, the cleaning blade (3) having the tension set (JIS K6262) of 2.5% is employed. Therefore, the reduction (attenuation) in the pushing force against the photoreceptors (PRy to PRk, B) is small even after the cleaning blade (3) is left as it is for a long time in the high-temperature and high-humidity atmosphere, and thus the cleaning performance can be assured.
Also, if the material of the cleaning blade (3) is selected with regard to the characteristics of the blade materials, as described above, the necessity for increasing the pushing force against the photoreceptors (PRy to PRk and the intermediate transfer belt (B) to assure the cleaning performance can be eliminated. Thus, since the cleaning performance can be maintained in all application circumstances, the worn amount of the photoreceptors (PRy to PRk) and the intermediate transfer belt (B) can be reduced. In addition, in the situation that the friction coefficient of the surfaces of the photoreceptors (PRy to PRk, B) is increased because the discharge product is adhered onto the surfaces of the photoreceptors (PRy to PRk, B) or the surfaces thereof are changed in quality, the noise (creaking) due to the vibration of the cleaning blade (3) can be reduced.
According to a third aspect of the invention, a cleaner for image carrying body, has a cleaning blade (3) having a blade top end portion for frictionally contacting with a surface of an image carrying body (PRy to PRk) to remove residual toners on the surface when the surface passes through a cleaning area. The cleaning blade (3) is made of elastic material. The cleaning blade (3) is formed of urethane rubber. A modulus of repulsion elasticity (JIS K6255) of the cleaning blade (3) is not less than 20% at 10xc2x0 C. and not more than 70% at 40xc2x0 C. A 300% modulus (JIS K6251) of the cleaning blade (3) is not less than 200 kgf/cm2. A tear strength (JIS K6252 crescent type) of the cleaning blade (3) is more than 35 kgf/cm. The cleaning blade (3) removes a toner adhering to the surface of the image carrying body (PRy to PRk) on which a toner image is formed.
The cleaner for the image carrying body of the present invention having the above configuration cleans the residual toners adhered onto the surfaces of the image carrying bodies (PRy, PRm, PRc, PRk, B) such as the photoreceptors (PRy to PRk), the intermediate transfer belt (B), by the cleaning blade (3).
According to a fourth aspect of the invention, an image forming apparatus has:
a photoreceptor (PRy to PRk);
a charging unit (CRy to CRk);
an electrostatic latent image formning unit (ROS);
a developing unit (Gy to Gk);
a transferring unit (T1y to T1k); and
a photoreceptor cleaner (CLy to CLk).
The photoreceptor (PRy to PRk) passes through a charging area in which a surface thereof rotating is charged, a latent image writing position (Q1y to Q1k) in which a light is irradiated thereto in response to an image, a developing area (Q2y to Q2k) opposing to the developing unit, a transferring area (Q3y to Q3k), and a cleaning area sequentially. The charging unit (CRy to CRk) charges a surface of the photoreceptor (PRy to PRk) passing through the charging area. The electrostatic latent image forming unit (ROS) forms an electrostatic latent image on the surface of the charged photoreceptors (PRy to PRk) passing through the latent image writing position (Q1y to Q1k). The developing unit (Q2y to Q2k) develops the electrostatic latent image on the surface of the photoreceptor (PRy to PRk) passing through the developing area (Q2y to Q2k) into a toner image. The transferring unit (T1y to T1k) transfers the toner image on the surface of the photoreceptor (PRy to PRk) passing through the transferring area (Q3y to Q3k) onto a transfer material. The photoreceptor cleaner (CLy to CLk) has the cleaning blade (3) and cleans a toner adhered to the surface of the photoreceptor (PRy to PRk) on which the toner image is formed by the cleaning blade (3). The cleaning blade (3) has a blade top end portion for frictionally contacting with the surface of the photoreceptor (PRy to PRk) to remove the toner adhering to the surface when the surface passes through the cleaning area. The cleaning blade (3) is made of elastic material. The cleaning blade (3) is formed of urethane rubber. A modulus of repulsion elasticity (JIS K6255) of the cleaning blade (3) is not less than 20% at 10xc2x0 C. and not more than 70% at 40xc2x0 C. A 300% modulus (JIS K6251) of the cleaning blade (3) is not less than 200 kgf/cm2. A tear strength (JIS K6252 crescent type) of the cleaning blade (3) is more than 35 kgf/cm.
According to a sixth aspect of the invention, in the image forming apparatus according to the fourth aspect, the developing unit (Gy to Gk) may employ a toner having shape factor SF less than 140. The shape factor SF is expressed by
SF=[M2/(Axc3x974xcfx80)]xc3x97100
where M is a maximum circumferential length of a toner particle and A is a projected area of the toner particle.
Since the image forming apparatus according to the fourth aspect of the invention, employs the cleaning blade (3) of the present invention, there is no necessity that the pushing force against the image carrying bodies (PRy to PRk, B) such as the photoreceptors (PRy to PRk) must be increased to assure the cleaning performance, and the worn amount of the photoreceptors (PRy to PRk) can be reduced since the cleaning performance can be assured in all application atmospheres.
Accordingly, assume that the maximum circumferential length of the toner particle is M and the projected area of the particle is A, an image with the high picture quality can be formed not to generate the defective cleaning even when the developing units (Gy to Gk) using the toners having shape factor SF expressed by SF=[M2/(Axc3x974xcfx80)]xc3x97100 less than 140 are employed.
According to a fifth aspect of the invention, an image forming apparatus of the present invention may have:
a photoreceptor (PRy to PRk);
a charging unit (CRy to CRk);
an electrostatic latent image forming unit (ROS);
a developing unit (Gy to Gk;
an intermediate transferring body (B);
a primary transferring unit (T1y to T1k);
a secondary transferring unit (T2); and
an intermediate transferring body cleaner (CLb).
The photoreceptor (PRy to PRk) passes through a charging area in which a surface thereof is charged, a latent image writing position (Q1y to Q1k) in which a light is irradiated thereto in response to an image, a developing area (Q2y to Q2k) opposing to the developing unit (Gy to Gk), a primary transferring area (Q3y to Q3k), and a photoreceptor cleaning area sequentially. The charging unit (CRy to CRk) charges the surface of the photoreceptors (PRy to PRk) passing through the charging area. The electrostatic latent image forming unit (ROS) forms an electrostatic latent image on the surface of the charged photoreceptor (PRy to PRk) passing through the latent image writing position (Q1y to Q1k). The developing unit (Gy to Gk) develops the electrostatic latent image on the surface of the photoreceptor (PRy to PRk) passing through the developing area (Q2y to Q2k) into a toner image. The intermediate transferring body (B) passes through the primary transferring area (Q3y to Q3k) in which the intermediate transferring body (B) comes into contact with the surface of the photoreceptor (PRy to PRk) and the toner image on the surface of the photoreceptor (PRy to PRk) is primarily transferred thereonto, a secondary transferring area (Q4) in which the toner image being primarily transferred is secondarily transferred onto a recording sheet (S), and the intermediate transferring body cleaning area in which a surface thereof is cleaned sequentially. The primary transferring unit (T1y to T1k) transfers the toner image on the surface of the photoreceptor (PRy to PRk) passing through the primary transferring area (Q3y to Q3k) onto the intermediate transferring body (B). The secondary transferring unit (T2) transfers the toner image on a surface of the intermediate transferring body (B) passing through the secondary transferring area (Q4) onto the recording sheet (S). The intermediate transferring body cleaner (CLb) has a cleaning blade (3) and cleans a toner adhering to the surface of the intermediate transferring body (B) by the cleaning blade (3) in the intermediate transferring body cleaning area. The cleaning blade (3) has a blade top end portion for frictionally contacting with the surface of the photoreceptor (PRy to PRk) to remove the toner adhering to the surface when the surface passes through the cleaning area. The cleaning blade (3) is made of elastic material. The cleaning blade (3) is formed of urethane rubber. A modulus of repulsion elasticity (JIS K6255) of the cleaning blade (3) is not less than 20% at 10xc2x0 C. and not more than 70% at 40xc2x0 C. A 300% modulus (JIS K6251) of the cleaning blade (3) is not less than 200 kgf/cm2. A tear strength (JIS K6252 crescent type) of the cleaning blade (3) is more than 35 kgf/cm.
According to a seventh aspect of the invention, in the image forming apparatus according to the fifth aspect of the invention, the developing unit (Gy to Gk) may employ a toner having shape factor SF less than 140. The shape factor SF is expressed by
SF=[M2/(Axc3x974xcfx80)]xc3x97100
where M is a maximum circumferential length of a toner particle and A is a projected area of the toner particle.
Since the image forming apparatus according to the fifth aspect of the invention, employs the cleaning blade (3) of the present invention, there is no necessity that the pushing force against the intermediate transferring body (B) must be increased to assure the cleaning performance, and the worn amount of the intermediate transferring body (B) can be reduced since the cleaning performance can be assured in all application atmospheres.
Accordingly, assume that the maximum circumferential length of the toner particle is M and the projected area of the particle is A, an image with the high picture quality can be formed not to generate the defective cleaning even when the developing units (Gy to Gk) using the toners having shape factor SF expressed by SF=[M2/(Axc3x974xcfx80)]xc3x97100 less than 140 are employed.
According to an eighth aspect of the invention, the image forming apparatus according to the fourth aspect of the invention may have:
a sheet carrying belt for carrying the recording sheet (S), on which the toner image formed on the surfaces of the photoreceptors (PRy to PRk) is transferred, into the transferring areas (Q3y to Q3k); and
a sheet carrying belt cleaner having the cleaning blade (3) according to the first or second aspect of the invention, and for cleaning the toners, which are adhered onto a surface of the sheet carrying belt, by the cleaning blade (3).
Since the image forming apparatus according to the eighth aspect of the invention, employs the cleaning blade (3) of the present invention, there is no necessity that the pushing force against the sheet carrying belt must be increased to assure the cleaning performance. Also, since the cleaning performance can be assured in all application atmospheres, the worn amount of the sheet carrying belt can be reduced. Accordingly, even if the developing units (Gy to Gk) using the toners having shape factor less than 140 are employed, an image with the high picture quality can be formed without the generation of the defective cleaning.
According to a ninth aspect of the invention, the image forming apparatus according to the fifth aspect of the invention may have a secondary transferring unit cleaner having the cleaning blade (3) and for cleaning the toners, which are adhered onto a surface of the secondary transferring unit (T2), by the cleaning blade (3).
Since the image forming apparatus according to the ninth aspect of the invention employs the cleaning blade (3) of the present invention, there is no necessity that the pushing force against the secondary transferring unit (T2) must be increased to assure the cleaning performance. Also, since the cleaning performance can be assured in all application atmospheres, the worn amount of the secondary transferring unit (T2) can be reduced. Accordingly, even if the developing units (Gy to Gk) using the toners having shape factor less than 140 are employed, an image with the high picture quality can be formed without the generation of the defective cleaning.